Macbook Pro 16 Thunderbolt Low Resolution 30Hz Debug

Discussion in 'Apple and Mac OS X' started by syngress, Jan 26, 2021.

  1. syngress

    syngress Notebook Enthusiast

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    I have some issue with my Macbook Pro 16 (BigSur).

    Below 4 Macbook Pro thunderbolt ports, for clarity, I numbered the TB ports.

    LID/LID/LID/LID/LID
    1 ------------------- 2
    3 ------------------- 4


    I try to connect 4K LG monitor directly via thunderbolt->thunderbolt cable.
    Now, mac gives me 720p max resolution with 30Hz on TB ports (2 and 4)
    On ports (1 and 3) i have 4k resolution but only 30Hz and screen is little bit blurry :-/
    Regardless of whether the GPU Switch is turned on (battery or power supply), the problem is the same.
    That will be some TB issue, when I connect monitor through TB->HDMI adapter i have no problem with 4K 60Hz resolution.

    Now same LG monitor and some other Macbook Pro 15 2017, same TB -> TB cable, 4k 60Hz no problem ...

    How can I debug what happen with 16" mac ?
     
    Last edited: Jan 26, 2021
  2. syngress

    syngress Notebook Enthusiast

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